Description
In the Linux kernel, the following vulnerability has been resolved: mptcp: fix NULL pointer in can_accept_new_subflow When testing valkey benchmark tool with MPTCP, the kernel panics in 'mptcp_can_accept_new_subflow' because subflow_req->msk is NULL. Call trace: mptcp_can_accept_new_subflow (./net/mptcp/subflow.c:63 (discriminator 4)) (P) subflow_syn_recv_sock (./net/mptcp/subflow.c:854) tcp_check_req (./net/ipv4/tcp_minisocks.c:863) tcp_v4_rcv (./net/ipv4/tcp_ipv4.c:2268) ip_protocol_deliver_rcu (./net/ipv4/ip_input.c:207) ip_local_deliver_finish (./net/ipv4/ip_input.c:234) ip_local_deliver (./net/ipv4/ip_input.c:254) ip_rcv_finish (./net/ipv4/ip_input.c:449) ... According to the debug log, the same req received two SYN-ACK in a very short time, very likely because the client retransmits the syn ack due to multiple reasons. Even if the packets are transmitted with a relevant time interval, they can be processed by the server on different CPUs concurrently). The 'subflow_req->msk' ownership is transferred to the subflow the first, and there will be a risk of a null pointer dereference here. This patch fixes this issue by moving the 'subflow_req->msk' under the `own_req == true` conditional. Note that the !msk check in subflow_hmac_valid() can be dropped, because the same check already exists under the own_req mpj branch where the code has been moved to.
Product status
9466a1ccebbe54ac57fb8a89c2b4b854826546a8 (git) before 8cf7fef1bb2ffea7792bcbf71ca00216cecc725d
9466a1ccebbe54ac57fb8a89c2b4b854826546a8 (git) before b3088bd2a6790c8efff139d86d7a9d0b1305977b
9466a1ccebbe54ac57fb8a89c2b4b854826546a8 (git) before 855bf0aacd51fced11ea9aa0d5101ee0febaeadb
9466a1ccebbe54ac57fb8a89c2b4b854826546a8 (git) before 7f9ae060ed64aef8f174c5f1ea513825b1be9af1
9466a1ccebbe54ac57fb8a89c2b4b854826546a8 (git) before dc81e41a307df523072186b241fa8244fecd7803
9466a1ccebbe54ac57fb8a89c2b4b854826546a8 (git) before efd58a8dd9e7a709a90ee486a4247c923d27296f
9466a1ccebbe54ac57fb8a89c2b4b854826546a8 (git) before 4b2649b9717678aeb097893cc49f59311a1ecab0
9466a1ccebbe54ac57fb8a89c2b4b854826546a8 (git) before 443041deb5ef6a1289a99ed95015ec7442f141dc
5.9
Any version before 5.9
5.10.237 (semver)
5.15.181 (semver)
6.1.135 (semver)
6.6.88 (semver)
6.12.24 (semver)
6.13.12 (semver)
6.14.3 (semver)
6.15 (original_commit_for_fix)
References
lists.debian.org/debian-lts-announce/2025/05/msg00045.html
lists.debian.org/debian-lts-announce/2025/05/msg00030.html
git.kernel.org/...c/8cf7fef1bb2ffea7792bcbf71ca00216cecc725d
git.kernel.org/...c/b3088bd2a6790c8efff139d86d7a9d0b1305977b
git.kernel.org/...c/855bf0aacd51fced11ea9aa0d5101ee0febaeadb
git.kernel.org/...c/7f9ae060ed64aef8f174c5f1ea513825b1be9af1
git.kernel.org/...c/dc81e41a307df523072186b241fa8244fecd7803
git.kernel.org/...c/efd58a8dd9e7a709a90ee486a4247c923d27296f
git.kernel.org/...c/4b2649b9717678aeb097893cc49f59311a1ecab0
git.kernel.org/...c/443041deb5ef6a1289a99ed95015ec7442f141dc